Two dimensional gel electrophoresis (2D-PAGE) is currently a method of choice for analysis of complex proteomes, permitting the separation, identification, and analysis of large numbers of proteins in a single multiplexed analysis.
Typically, first dimension separation is performed by isoelectric focusing within the gel of an immobilized pH gradient (IPG) strip. Subsequent equilibration, typically by contacting the IPG strip with fluid buffers variously containing reducing and alkylating agents, prepares the focused proteins for second dimension size separation on a polyacrylamide gel.
The recent development of cassettes within which IPG strips can be hydratingly lodged during focusing—as described for example in U.S. patent application publication No. 2003/0015426 and international patent publication no. WO 02/092200, and available commercially from Invitrogen Corp. as the ZOOM® IPGRunner™ system—has significantly simplified first dimension separation.
Notwithstanding these improvements during first dimension separation, however, the subsequent step of equilibration requires that IPG strips be individually removed from the cassette and placed in separate tubes, within which they can be equilibrated in preparation for second dimension separation. The tubes add cost, and handling the strips increases the chance of damage to the strips and the gels thereon, with consequent loss of analytical resolution.
There thus exists a need in the art for apparatus and methods that permit the contact of cassette-immobilized gels to fluids, such as equilibration fluids, without requiring their removal from the cassettes within which or upon which they are immobilized.